1. Field of the Invention
The invention relates to the loading of vessels with absorbent material. More particularly, it relates to the loading of adsorbents so as to achieve a uniform packing thereof throughout the vessels.
2. Description of the Prior Art
In the practice of the pressure swing absorption (PSA) or thermal swing adsorption (TSA) technology in which a more readily adsorbable component of a feed gas is selectively adsorbed in a bed of adsorbent material, the overall performance achieved is sometimes less than expected and desired for practical commercial applications. One cause for such sub-par performance is a non-uniform density of the adsorbent particles in adsorbent vessels resulting from the particle loading techniques commonly employed in the art.
For example, adsorbent particles are commonly transferred from a shipping drum into a processing vessel by simple dumping of the adsorbent material from the shipping drum into the vessel through a top flange portion thereof. The adsorbent material flows into the vessel and forms a cone generally in the center portion thereof, with adsorbent particles reaching the wall of the vessel by sliding down the sides of the cone and outward toward said wall. This particle loading approach results in a center region of high particle packing density, an outer region close to the vessel wall of lower particle packing density, and an intermediate, variable density region.
In order to overcome this non-uniform particle packing density, a series of deflector cones having a center hole have been placed in the vessel immediately under the inlet opening thereof. As the adsorbent particles being loaded flow into the vessel, they strike the cones and are deflected in an outward direction toward the wall of the vessel. This approach tends to spread the particles out from the center cone, and to create a somewhat more uniform particle packing density. It has not been found to be effective, however, with respect to larger sized, commercially significant vessels having diameters of over about 6 feet, some of the flowing particles do not have sufficient energy to enable them to be dispersed to the outer region at the wall of the vessel. This approach is also disadvantaged by its need to accurately position a uniform inlet stream of particles in the center of the series of cones. This is very difficult to achieve since the particles are being powered from a large drum, e.g. a 55 gallon drum, through a flexible hose into the inlet flange of the vessel.
As those skilled in the art will appreciate, another set of problems can also arise in vessel loading due to drum-to-drum variations in the particles being loaded, and the particular method of loading employed. If, for example, the particles are poured into the vessel in accordance with common practice, it has been observed that all of the material from one shipping drum will tend to collect in one area of the bed. This material may be more or less reactive, or somewhat larger or smaller in size, than the overall average of the bed. This also will result in areas of adsorbent material non-uniformity in the bed, which will decrease the efficiency of the adsorption process carried out in the vessel.
If, for the reasons indicated above, a non-uniform particle packing exists in an adsorption vessel, a non-uniform flow of fluid therethrough will be observed. Thus, as the fluid approaches the bed of particle material at a uniform pressure, either at the top or the bottom of the adsorbent bed, the flow of such fluid will be less through the dense central region thereof than through the looser, less densely packed outer edge sections thereof. Such variation in particle density from the center to the outer edge portion of the bed will generally be greater as the diameter of the vessel is increased. This results from the greater shearing action the particles undergo as they move from the center to the outer edge of the adsorbent bed in the vessel. In this regard, it should be noted that, for relatively small sized vessels, e.g. in the 1 to 4 feet diameter range, nearly uniform densities can be achieved because the center region of the particle cone will nearly fill the entire vessel. For larger vessels, however, the center region of the particle cone will not fill the entire vessel and non-uniform packing of the particles will be observed. In such large vessels, it has also been observed that small variations in bed density can lead to large changes in the velocity of gas flow through the bed since said velocity through the packed bed is a strong function of the particle packing density. It is such non-uniform flow conditions, caused by a non-uniform packing of particles in the vessel, that results in the above-indicated disappointing levels of adsorption performance that can be encountered in larger size, commercially significant operations.
In light of these circumstances, there is a genuine need for further development of the particle loading techniques used in commercial practice. In particular, there is a need for such development leading to a more uniform packing of adsorbent particles, especially for use in the loading of larger sized adsorption vessels.
It is an object of the invention, therefore, to provide an improved apparatus for the loading of adsorption vessels.
It is another object of the invention to provide an apparatus for achieving a uniform packing of adsorbent throughout an adsorption vessel.
With these and other objects in mind, the invention is hereinafter described in detail, the novel features thereof being particularly pointed out in the appended claims.